320 A VEGETABLE MONSTER. Book II. 
hues of lilac and violet, with deep blue shadows, so that 
they resembled a mass of solid lepidolite. 
We encamped for the night where the terrace begins to 
slope in a southerly direction. When we rose, at 3 a.m., the 
plain was white with hoar frost. On our way we set fire 
to the dry leaves of some yuccas, which burned with a high 
crackling flame, enclosing the whole stem, and affording us 
considerable warmth as we passed. By the time the sun 
had risen we had reached the valley. Our early march in 
the dark prevented my examining the afore-named isolated 
group of rocks, which, in a geological point of view, must 
be very interesting. If I was not deceived by the distance, 
volcanic, plutonic, metamorphic, and sedimentary rocks 
are compressed into a small space here, and easily to be 
examined; the whole representing quite a small geological 
laboratory. 
By the river the scenery was equally interesting. A 
lofty, precipitous, rocky mountain, towered on the other 
side of the valley. Poplars grew on the plain, and the 
sandy hill by which we had descended was covered with 
tall yuccas and many varieties of shrubs ; while behind this, 
to the east, the distant peaks of the loftier mountains arose, 
looking surprisingly near. Here for the first time I saw 
the gigantic Echinocactus Wislizeni, a perfect vegetable 
monster. Let the reader imagine a barrel-shaped, deeply- 
ribbed, green mass, from three to four feet high, and from 
two to three feet thick, covered with bunches of thorns 
long and strong enough to inflict a deadly wound ; the 
centre ones of each bunch being curved, so as to form 
perfect hooks. The rock of the precipice along which the 
road passes is sandstone, exhibiting the influence of volcanic 
agencies. The mountain on the opposite side of the valley 
appears to be of the same formation. The fragments of 
